1. Field of the Invention
The present invention relates to an automotive muffler, and more particularly to an automotive muffler operating both in a circuitous and in a straight way. Meanwhile, the output horsepower can be enhanced.
2. Description of the Related Art
The exhaust ejected from the internal combustion engine and directly injected into the atmosphere will produce a harsh noise since the gas pressure of the exhaust is suddenly reduced from a high level to an atmospheric level. Thus, the exhaust has to pass through a sound-deadening unit for reducing the pressure and the frequency of the exhaust, thereby efficiently lowering the exhaust noise.
A conventional automotive muffler 10, as shown in FIG. 1, operates in a circuitous way. The circuitous muffler includes partitions 12 within a cylindrical body 11 for separating a plurality of gas chambers 13. A plurality of the air guide tubes 14 are interconnected to one another within the gas chambers 13 according to a circuitous design. A plurality of vent holes 141 are formed in the air guide tubes 14 according to different requirements. In this way, the exhaust passing through the vent holes 141 is expanded. Moreover, the high-pressure exhaust ejected from the engine and illustrated by arrows in FIG. 1 passes through all of the air guide tubes 14 and is expanded within all of the gas chambers 13 for ensuring the pressure relief and achieving the sound-deadening effect.
As shown in FIG. 2, a straight-way type muffler 20 includes a cylindrical body 21 in which an internal tube 22 with a plurality of vent holes 221 is disposed. The internal tube 22 is enclosed by the cylindrical body 21. A sound-absorbing chamber defined by the periphery of the internal tube 22 and the internal wall of the cylindrical body 21 is filled with sound-absorbing material 23. In this way, the exhaust ejecting from the engine and passing through the internal tube 22 will be expanded by means of the vent holes 221 for reducing the exhaust pressure. Meanwhile, the sound-absorbing material 23 filled within the sound-absorbing chamber is used to absorb the exhaust sound. In this way, a sound-deadening effect is achieved.
The above-mentioned automotive mufflers have their own advantages and disadvantages. The circuitous muffler has the problem of great return pressure due to the complicated flowing path of exhaust. However, it has an excellent sound-deadening effect. The straight-way type muffler 20 has smaller return pressure and is beneficial for high-velocity gas exhaust due to the simple and smooth exhaust path. However, the straight-way type muffler 20 has difficulties in absorbing the exhaust sound, thereby causing noise problem.
In fact, the engine is an air pump. Its efficiency greatly depends upon how easily the gas is injected and ejected. The resistance in ejecting and injecting the gas is called as “pumping loss”. Evidently, the smaller the resistance is, the less the pumping loss is caused. As a result, a greater horsepower can be achieved. The exhaust system must maintain the least resistance of the exhaust gas flow for maximizing the power horse. This resistance prevents the exhaust from blowing out of the engine, thereby resulting in dilution of the fresh oil vapor entering into the engine afterward. In other words, one part of the exhaust remains within the cylinder and is mixed with fresh oil vapor, thereby affecting the performance of engine. Even, a return pressure will be created when the resistance becomes greater. The engine must give more effort to eject the exhaust from the cylinder. This is one of the sources of the pumping loss.
Accordingly, the conventional circuitous muffler and the straight-way type muffler have their own advantages and disadvantages. They can not fulfill the requirements of low noise and maximal horsepower. Accordingly, they require further improvements.